1. Field of the Invention
The invention relates generally to detecting radiation levels in radiation therapy and, more particularly, to an apparatus and method for detecting, measuring and altering dosage levels in external beam radiation treatments.
2. Related Art
External beam radiation modalities are the most common treatment and imaging tools for cancer management. In external beam radiation modalities, a beam consisting of photons, electrons or heavier particles (protons are ions) are used to either treat or image cancer tumors. External beam radiation modalities may be used for a wide range of diseases, including, for example, cancer tumors (localized or not localized), assessment of bone structures, and visualization of objects within a body or similar conditions.
Using prostate cancer as an example, there are currently three types of external beam radiation modalities suitable for treating prostate cancer: photon irradiation, proton irradiation and ions irradiation. Each offering various advantages with respect to each other. The patient usually lays on a bed for this treatment and undergoes a two-stage process: an imaging step to assess the location and size of the tumor and a treatment step to eliminate the cancer cells. The first step is primarily performed through the use of photons via X-ray or computerized tomography (CT) scans.
Currently, only post-irradiation techniques are used to provide a crude assessment of the dose delivered to patient in external beam therapy. Recent clinical studies also indicate that some cancers may be caused during the imaging process. There is currently no method for measuring the real-time multi-dimensional tissue dose distribution. Instead, tissue density mapping may be obtained from magnetic resonance imaging and x-ray computed tomography. These tissue density maps are often utilized in combination with the total beam fluency, beam positions and irradiation times, in Monte Carlo simulations to calculate the dose distribution in tissue. However, relying on simulations does not provide any actual measured dose distribution and therefore any over or under exposure is typically determined post therapy by the physiological response. Without ability to measure actual dosage distribution during external beam radiation modalities, adjustments of the dose distribution cannot be made during treatments so that a more desired effect can be achieved such as assuring more effective targeting of tumors, or avoiding/minimizing irradiation of nearby healthy tissue.
Accordingly, there is a need to be able to characterize the radiation beam to aid in creating an external beam radiation treatment plan based on the characterized beam radiation source. Furthermore, there is a need to a have a way to measure actual radiation dosages delivered in external beam radiation modalities when using the characterized beam radiation source to determine tissue dosimetry so that a way of altering the treatment plan, based on the actual measurements, might be achieved. In this way, a desired dosage level and distribution of radiation might be more accurately delivered during the course of treatment.